hey guys i have a 94 vx with a gsr swap and chipped p28.
my questions is does the p28 search for a secondary o2 or just a single, i currently dont have any o2s and it throwing my cel because of it?
do i have to install both or just a single?

 

that car, that computer, that half of the decade...

only looks for one o2

however.. the vx uses a five wire o2.. the p28 and everything else in the modern world uses a 4 wire o2. prolly your problem there

 

careful with that statement, a lot of newer cars have widebands stock now...

Provided you have an OBD1 P28 (yes there are OBD2 versions but they are rare)
The P28 looks for one O2 (primary), and it really depends on which code you're getting. 41 or 1?

 

BUMP!! 4 a QUESTION?

I want to know if I need to have 2 O2 sensors using a chipped P28 ecu in a 99 civic with a B16? Or just one primary one will do?

 

the obd1 ecu in ur obd2 car wont look for a 2nd o2. The primary is all u need

 

no just primary.

 

How would I tell which plug is primary and which is secondary?

Or just check both?

 

If youre P28 was OBD1 then 1 sensor, if OBD2, then 2 sensors.
The primary sensor is the one closest to the engine, sometimes they are on your header and sometimes theyre right after the header. The secondary would be whichever came after that depending on where the hole for it is.

 

No I'm not stupid, learning is becoming smart.

So both my plugs for the O2 are in the back. The harness is from a EX.

I know the closest one to motor is the primary, but these are just plugs hanging, so I wouldn't be able to tell which one is primary and which one is secondary.

The only way I would check is, plug it in turn the motor on look for CEL if 1 or 41 code try the other plug correct?

 

Yeah my bad for that, I soon realized you werent the original poster. The thread jack threw me off. Why are your o2 sensors in the back? What kind of header do you have? If you have a header heat shield, then take it off and you will be able to see it.

I know that the plug thats right on top of the tranny is the one for primary. No idea where your other plug is but that should be the secondary. Reason i say the plug on top of the tranny close to the block is the primary is bc its the one closest to the header which if its stock, would be for that o2 sensor that goes there.

 

It's arri' man!!

So my O2 sensor wiring is pretty much done!!! Well I would also like to know what connections should be?

I have an EX EWH so there is only 1 PRIMARY O2 sensor wire on the EWH so thats fine.

Thats pretty much it for the O2.